a systematic means of communicating by the use of sounds or conventional symbols

The reconstructed ancestor language or protolanguage of the Indo-European family of languages, which includes most European and Indian languages.

An undocumented hypothetical language from which all the Slavic languages later emerged.

a North Germanic language spoken in in Shetland (Hjatland), Orkney and Caithness in mainland Scotland until the 19th century.

the form of the Polish language used between the 9th and the 16th centuries.